The nation's most innovative metro areas — as measured by the number of patents granted in the community — enjoy the strongest economies, according to a Brookings Institution study out today.

"A strong innovation system is a critical contributor to prosperity," says Brookings senior fellow Mark Muro, an author of the report.

The San Jose-Sunnyvale-Santa Clara area — home to tech giants such as Apple, Google and Intel — by far tops the nation in patents overall and per million residents. The Research Triangle in North Carolina is also in the top 20 in patents per million residents. But so are less-obvious areas that quietly host high-tech firms or research universities, such as Burlington, Vt.; Rochester, Minn.; Corvallis, Ore.; Boulder, Colo.; and Albany-Schenectady-Troy, N.Y.

Many patents are used to develop new products or improvements, yielding profits and licensing fees for the companies, universities or individuals who own them. Sometimes they lead to new local design, engineering or manufacturing operations.

Those pillars of local economies are typically more valuable in the long run than housing booms, retail centers and sports complexes that may rise and fall in volatile cycles, says Brookings associate fellow Jonathan Rothwell.

Also, he says, such consumption-oriented industries as sports stadiums typically attract local money that's siphoned from another area activity. New products or technologies draw fresh cash from around the nation and the world. Workers who invent or make them, in turn, spend what they earn on local services, further growing the economy.

"All that (revenue from Apple iPhone sales) is money that otherwise never would get to the San Jose metro area," he says.

The study found that patents are slightly more relevant to an area's growth in productivity, or wages and profits per worker, than its proportion of college graduates. But they're less relevant than a large population or high employment in a wealth-producing industry, such as energy.

Fourteen of the 20 areas with the biggest increases in patents per worker from 1980 to 2010 also had above-average productivity growth. Four — Corvallis, Ore.; Boulder, Colo; Raleigh, N.C.; and Portland, Ore. — rank in the top 20 in productivity growth.

The 10 metro areas with the fastest patent growth from 1990 to 2010 had an average unemployment rate of 4.9%, vs. 6.2% for large metro areas with slow patent growth.

While some smaller communities are big patent producers, 63% of patents are developed by inventors in 20 mostly large metro areas with 34% of the population, the study found. Big metro areas allow inventors to specialize more, Rothwell says.

How can a region become a patent hub? Areas that churn out lots of patents tend to have at least several graduate research programs, a tech-oriented workforce and a large number of inventors per patent, the study says. Patents owned by universities and funded by federal grants often foster such collaboration.

Burlington, for example, has an IBM chip plant and the University of Vermont. Rochester, Minn., has an IBM facility and the Mayo Clinic.

Corvallis has a Hewlett-Packard research center; Boulder is a tech hub; and Albany, N.Y., has GE's global research headquarters.

All those areas rank among the top 20% of metro areas in the technology skills of their workforces and average number of inventors per patent.